Potential Transmission of BSE to Humans

Epidemiologic and laboratory evidence suggests that the BSE agent has been transmitted to humans via consumption of BSE-contaminated cattle products, causing nvCJD. However, the risk for acquiring vCJD from consumption of BSE-contaminated product is low, presumably because of a species barrier that provides some degree of protection against development of nvCJD. BSE is the only TSE of animals that has ever been linked with human disease. In the United Kingdom, where an estimated 1 million or more cattle probably were infected with BSE, cases of nvCJD continue to be reported; however, the number of cases of nvCJD remains small, with 147 probable and confirmed vCJD cases identified as of August 2004, including those of three persons residing in Ireland, Canada, and the United States who are believed to have been exposed to BSE in the United Kingdom. No cases of nvCJD have been identified where the patient did not have exposure within a country where BSE was occurring (96-100).